1. Field of the Invention
The present invention relates to a lens driving device used by a camera loaded in a mobile phone.
2. Description of Related Art
In recent years, mobile phones have various functions of internet communication, games and the like besides photographic function (cameras), so that the power consumption is increased. Moreover, in electromagnetic drive type lens driving device used for cameras, besides the function of auto focus, the structure with the function of shaking correction is also added, and the power consumption in the lens driving device is also increased.
PCT patent application publication NO. WO2010/043078A1, Pub. date of Apr. 22, 2010 discloses a lens driving device as shown in FIG. 6A to 6D. FIG. 6A is a perspective view of a lens driving device 30, FIG. 6B is an exploded view of the lens driving device 30, FIG. 6C is a perspective view of the main parts of an electromagnetic drive mechanism 31 in the lens driving device 30, and FIG. 6D is a schematic diagram illustrating the magnetic field generated by drive magnets 31M. Hereon, the optical axis direction of a lens 35 is set to be the Z axis direction (the object to be shot is at +Z side), and two directions forming right angles with Z axis and perpendicular to each other are set to be X axis direction and Y axis direction respectively. Moreover, in FIG. 6C, the aftermentioned +X side drive magnet 31MPX is partially illustrated through cutting so as to improve the visibility of the oppositely arranged +X side drive coil 31CPX.
The lens driving device 30 includes the functions of auto focus and shaking correction, so that the lens 35 moves along the Z axis direction, a shot image is focused in an unshown image sensor arranged at the back of the Z axis of the lens, and the lens 35 swings towards the X axis direction and the Y axis direction (for example, the lens 35 also swings towards the periphery of the axis parallel to the X axis and the periphery of the axis parallel to the Y axis respectively while rotating), so that the shot image in the image sensor is inhibited from shifting (camera shaking).
As shown in FIG. 6A, the lens driving device 30 is integrally formed in the shape of a cuboid, and the lens 35 is maintained at the central part of the lens driving device 30. As shown in FIG. 6B, the lens driving device 30 includes a lens support 32 for mounting the lens 35, two platelike spring components 34 for supporting the lens support 32 in a suspended manner to be capable of moving, an electromagnetic drive mechanism 31 composed of the drive coils 31C and the drive magnets 31M, and a square frame-shaped magnet support 33 for supporting the drive magnets 31M.
As shown in FIG. 6B and FIG. 6C, the drive coils 31C are composed of the following components: a +X side drive coil 31CPX which winds around the axis parallel to the X axis and is mounted on the +X side of the lens support 32, a −X side drive coil 31CMX which winds around the axis parallel to the X axis and is mounted on the −X side of the lens support 32, a +Y side drive coil 31CPY which winds around the axis parallel to the Y axis and is mounted on the +Y side of the lens support 32, and a −Y side drive coil 31CMY which winds around the axis parallel to the Y axis and is mounted on the −Y side of the lens support 32.
As shown in FIG. 6C, the drive magnets 31M are composed of the following components: a +X side drive magnet 31MPX which is mounted in the +X side square frame of the magnet support 33 and is isolated from the +X side drive coil 31CPX at an interval along the X axis direction and is arranged opposite to the +X side drive coil 31CPX, a −X side drive magnet 31MMX which is mounted in the −X side square frame of the magnet support 33 and is isolated from the −X side drive coil 31CMX at an interval along the X axis direction and is arranged opposite to the −X side drive coil 31CMX, a +Y side drive magnet 31MPY which is mounted in the +Y side square frame of the magnet support 33 and is isolated from the +Y side drive coil 31CPY at an interval along the Y axis direction and is arranged opposite to the +Y side drive coil 31CPY, and a −Y side drive magnet 31MMY which is mounted in the −Y side square frame of the magnet support 33 and is isolated from the −Y side drive coil 31CMY at an interval along the Y axis direction and is arranged opposite to the −Y side drive coil 31CMY.
The +X side drive magnet 31MPX, the −X side drive magnet 31MMX, the +Y side drive magnet 31MPY and the −Y side drive magnet 31MMY are respectively and completely cut into two parts: a cuboid-shaped +Z side magnet plate 31MA positioned in the +Z direction and a cuboid-shaped −Z side magnet plate 31MB positioned in the −Z direction.
The +X side drive coil 31CPX, the −X side drive coil 31CMX, the +Y side drive coil 31CPY and the −Y side drive coil 31CMY are respectively wound in the shapes of long circles, are arranged opposite to each other as a +Z side coil side 31CA and a +Z side magnet plate 31MA on one long side, and are arranged opposite to each other as a −Z side coil side 31CB and a −Z side magnet plate 31MB on the other long side.
The platelike spring component 34 is formed in the shape of a universal joint, and is composed of a +Z side platelike spring component 34F and a −Z side platelike spring component 34B. The inner diameter part 34a of the +Z side platelike spring component 34F is connected with the +Z side end part of the lens support 32, and the outer diameter part 34b of the +Z side platelike spring component 34F is connected with the +Z side end part of the magnet support 33. The inner diameter part 34a of the −Z side platelike spring component 34B is connected with the −Z side end part of the lens support 32, and the outer diameter part 34b of the −Z side platelike spring component 34B is connected with the −Z side end part of the magnet support 33. As a result, when the platelike spring components 34 straightly moves towards the Z axis direction, the platelike spring component 34 is used for supporting the lens support 32 in the suspended manner so that the lens support 32 rotates in the axis direction forming a right angle with the Z axis, and the platelike spring component 34 can swing along with the lens support 32.
As shown in FIG. 6C, the +Z side magnet plate 31MA and the −Z side magnet plate 31MB face the coil side 31CA and the coil side 31CB which are oppositely arranged.
Specifically, the +Z side magnet plate 31MA of the +X side drive magnet 31MPX faces the +Z side coil side 31CA of the +X side drive coil 31CPX, is magnetized along the X axis direction, so that the side of the +Z side coil side 31CA becomes an N pole. The −Z side magnet plate 31MB of the +X side drive magnet 31MPX faces the −Z side coil side 31CB of the +X side drive coil 31CPX, is reversely magnetized along the X axis direction, so that the side of the −Z side coil side 31CB becomes an S pole. The +Z side magnet plate 31MA of the −X side drive magnet 31MMX faces the +Z side coil side 31CA of the −X side drive coil 31CMX, is magnetized along the X axis direction, so that the side of the +Z side coil side 31CA becomes the N pole. The −Z side magnet plate 31MB of the −X side drive magnet 31MMX faces the −Z side coil side 31CB of the −X side drive coil 31CMX, is magnetized along the X axis direction, so that the side of the −Z side coil side 31CB becomes an S pole. The +Z side magnet plate 31MA of the +Y side drive magnet 31MPY faces the +Z side coil side 31CA of the +Y side drive coil 31CPY, is magnetized along the Y axis direction, so that the side of the +Z side coil side 31CA becomes the N pole. The −Z side magnet plate 31MB of the +Y side drive magnet 31MPY faces the −Z side coil side 31CB of the +Y side drive coil 31CPY, is magnetized along the Y axis direction, so that the side of the −Z side coil side 31CB becomes an S pole. The +Z side magnet plate 31MA of the −Y side drive magnet 31MMY faces the +Z side coil side 31CA of the −Y side drive coil 31CMY, is magnetized along the Y axis direction, so that the side of the +Z side coil side 31CA becomes the N pole. The −Z side magnet plate 31MB of the −Y side drive magnet 31MMY faces the −Z side coil side 31CB of the −Y side drive coil 31CMY, is magnetized along the Y axis direction, so that the side of the −Z side coil side 31CB becomes an S pole.
As mentioned above, the electromagnetic drive mechanism 31 is composed of the following four groups of components: an electromagnetic drive mechanism 31PX on the +X side composed of the +X side drive coil 31CPX and the +X side drive magnet 31MPX, an electromagnetic drive mechanism 31MX on the −X side composed of the −X side drive coil 31CMX and the −X side drive magnet 31MMX, an electromagnetic drive mechanism 31PY on the +Y side composed of the +Y side drive coil 31CPX and the +Y side drive magnet 31MPY, and an electromagnetic drive mechanism 31MY on the −Y side composed of the −Y side drive coil 31CMY and the −Y side drive magnet 31MMY.
As shown in FIG. 6D, the electromagnetic drive mechanism 31PX on the +X side and the electromagnetic drive mechanism 31MX on the −X side are open magnetic circuits composed of the +Z side magnet plate 31MA and the −Z side magnet plate 31MB which are adjacent along the Z axis direction, wherein the inner diameter side (the side of the +X side drive coil 31CPX and the −X side drive coil 31CMX in the figure) and the outer diameter side of the drive mechanism 31 are opened.
Namely, on the inner diameter side of the electromagnetic drive mechanism 31, magnetic induction lines sent from the +Z side magnet plate 31MA are expanded towards the inner diameter direction of the electromagnetic drive mechanism 31 and are crossed with the +Z side coil side 31CA, and then the direction of the magnetic induction lines is changed into the outer diameter direction of the electromagnetic drive mechanism 31, so that the magnetic induction lines are crossed with the −Z side coil side 31CB and are returned to the −Z side magnet plate 31MB. Moreover, on the outer diameter side of the electromagnetic drive mechanism 31, magnetic induction lines sent from the −Z side magnet plate 31MB to the outer diameter direction of the electromagnetic drive mechanism 31 are changed into the direction facing inner diameter, and are returned to the +Z side magnet plate 31MA. And then, in the electromagnetic drive mechanism 31PX on the +X side and the electromagnetic drive mechanism 31MX on the −X side, the magnetic induction intensity sent from the inner diameter side (the side of the +X side drive coil 31CPX and the −X side drive coil 31CMX) of the electromagnetic drive mechanism 31 and the magnetic induction intensity sent from the outer diameter side of the electromagnetic drive mechanism 31 are approximately same in degree.
For example, when current in the −X axis direction (anticlockwise direction in +X axis direction) flows in the +X side drive coil 31CPX in the electromagnetic drive mechanism 31PX on the +X side, lorentz force in the +Z axis direction is generated on the +Z side coil side 31CA of the +X side drive coil 31CPX, and lorentz force in the +Z axis direction is also generated on the −Z side coil side 31CB. Moreover, when current in the +X axis direction flows in the −X side drive coil 31CMX in the electromagnetic drive mechanism 31MX on the −X side, lorentz force in the +Z axis direction is generated on the +Z side coil side 31CA of the −X side drive coil 31CMX, and lorentz force in the +Z axis direction is also generated on the −Z side coil side 31CB.
Right now, if the current intensity when the +X side drive coil 31CPX is electrified is the same as the current intensity when the −X side drive coil 31CMX is electrified, the lens support 32 straightly moves towards the +Z axis direction; and if the current intensity when the +X side drive coil 31CPX is electrified is different from the current intensity when the −X side drive coil 31CMX is electrified, the lens support 32 straightly moves towards the +Z axis direction based on different electric quantities, and at the same time, the lens support 32 rotates and swings around the axis parallel to the Y axis (namely rotates and swings in the Y axis direction).
Similarly, when current in the −Y axis direction (anticlockwise direction in +Y axis direction) flows in the +Y side drive coil 31CPY in the electromagnetic drive mechanism 31PY on the +Y side, lorentz force in the +Z axis direction is generated on the +Z side coil side 31CA of the +Y side drive coil 31CPY, and lorentz force in the +Z axis direction is also generated on the −Z side coil side 31CB. Moreover, when current in the +Y axis direction flows in the −Y side drive coil 31CMY in the electromagnetic drive mechanism 31MY on the −Y side, lorentz force in the +Z axis direction is generated on the +Z side coil side 31CA of the −Y side drive coil 31CMY, and lorentz force in the +Z axis direction is also generated on the −Z side coil side 31CB.
Right now, if the current intensity when the +Y side drive coil 31CPY is electrified is the same as the current intensity when the −Y side drive coil 31CMY is electrified, the lens support 32 straightly moves towards the +Z axis direction; and if the if the current intensity when the +Y side drive coil 31CPY is electrified is different from the current intensity when the −Y side drive coil 31CMY is electrified, the lens support 32 straightly moves towards the +Z axis direction based on different electric quantities, and at the same time, the lens support 32 rotates and swings around the axis parallel to the X axis (namely rotates and swings in the X axis direction).
In this way, the electromagnetic drive mechanism 31 can start the functions of auto focus and shaking correction at the same time, so that the lens 34 maintained on the lens support 32 straightly moves towards the Z axis direction, and rotates and swings in the direction forming the right angle with the Z axis.
However, in the electromagnetic drive mechanism 31 formed as mentioned above, the efficiency of applying magnetic force is relatively low, and thus a magnetic field cannot be applied for the drive coils 31C sufficiently. Moreover, as mentioned above, the electromagnetic drive mechanism 31 needs to carry out the operation of the two functions of auto focus (the lens 35 moves along the Z axis direction) and shaking correction (the lens 35 swings in the X axis direction and the Y axis direction), so that the power consumption is increased compared with a lens driving device with the function of auto focus only. Therefore, the operation of the electromagnetic drive mechanism 31 during the shooting of the camera needs a large amount of electric power, so that the problem that the consumption time of a rechargeable battery loaded in a mobile phone becomes short appears. Therefore, an electromagnetic drive mechanism with low power consumption is needed.